1. Field of the Invention
The present invention relates to bearings, such as roller bearings, journal bearings, sleeve bearings and the like, used to support rotating shafts in turbomachinery such as compressors and turbines and, more particularly, a bearing assembly including a squeeze film damper with a support structure for centering support of a bearing within the squeeze film damper annulus.
2. Description of Related Art
Large axial and radial forces act on high-speed rotors, such as the shafts of compressors or turbines, and these forces are compensated for by appropriately configured and arranged thrust bearings and journal bearings. In addition, it is also necessary to provide compensation for the radial rotor vibrations if trouble-free operation of such turbomachinery is to be ensured. For this purpose, squeeze film dampers are often employed in turbomachines to reduce the amplitude of the rotor vibrations. Typically, a squeeze film damper consists essentially of an annular gap configured between a bearing and a bearing support that is connected to an oil supply. The bearing may be a roller bearing, or may be of the hydrodynamic bearing type with hydrodynamic lubricating film on the shaft side, or may be any other bearing that supports a rotating shaft. The bearing may or may not be assembled into a sleeve. The bearing or bearing and sleeve may be referred to as a floating sleeve. In the case of a floating sleeve located within the annular gap of a squeeze film damper, the problem arises, particularly in the case of heavy rotors, that the floating sleeve is not centered in the annular gap during operation. Rather, the floating sleeve is positioned in the lower region of the bore in which it is situated. This arrangement can lead to poor damping properties and, further, to wear of the corresponding components.
Numerous possibilities for centering a floating sleeve within a squeeze film damper are known to avoid these disadvantages. One arrangement uses centering O-rings in the annular region of the squeeze film damper. Another arrangement uses centering provided by means of a lateral spring rod cage and by means of leaf springs arranged radially and locally at the periphery. A further squeeze film damper centering arrangement uses bending rods arranged radially at the outside periphery. A disadvantageous feature of O-ring centering, however, is that this arrangement has a nonlinear spring characteristic and unsatisfactory long-term behavior whereas, in the case of the spring rod cage, a very large amount of axial installation space is necessary. Moreover, bending rods require a large amount of radial space and, because of the large number of individual parts, are high cost and often deliver unsatisfactory concentricity accuracy. The leaf spring solution, which likewise requires a large amount of radial space, can only be manufactured by an electrical discharge machining method. In this case, furthermore, there is danger of shaft-side deformation of the bearing sleeve.
Based on the foregoing, there is considerable room for improvement in the field of bearing design and in the design of squeeze film dampers, particularly spring-backed or aided squeeze film dampers. The invention disclosed herein provides an improved and flexible structural support for centering a floating sleeve in a squeeze film annulus and overcomes many of the foregoing disadvantages found in current bearing and squeeze film damper design.